The present invention relates generally to the field of broadband power amplifiers. The present invention more particularly relates to broadband power amplifiers used with high peak-to-average power ratio waveforms.
Conventional broadband power amplifiers which must be used with high peak-to-average power ratio (PAPR) waveforms, such as orthogonal frequency division multiplexing (OFDM) and wideband code division multiple access (WCDMA) amplifiers exhibit power efficiencies well under 20%. This low level of power-efficiency forces significant system limitations in size, weight, operating time (duty cycle), and the number of simultaneous signals which can be transmitted from a platform (e.g., airplane, mobile ground vehicle, helicopter, human-portable communication device, etc.) due to serious thermal constraints.
Various limited solutions exist when operation can be restricted to a narrow range of frequencies (e.g., five percent bandwidth around operating frequency). Maintaining the necessary tolerances for successful operation of some of the solutions across an octave frequency range remains a daunting challenge. Across a wide range (e.g., 225 MHz to 400 MHz) a good option does not exist for achieving high amplifier power-efficiency with high peak-to-average power ratio waveforms.
Despite power efficiency problems with complex PAPR waveforms, the need for these waveforms remains high because they offer high spectral-efficiency; their theoretically sharp knife-edge frequency roll-off at the channel edges enables more users to operate within a given window of the RF spectrum. Theoretically, WCDMA and OFDM allow users to operate in immediately adjacent channels without experiencing interference. However, these waveforms produce no interference in adjacent channels only if near-ideal amplifiers are used for transmission.
What is needed is a power amplification system and method that improves efficiency of the amplifier, covers wide frequency bands, and is suitable for handling multiple waveforms with low levels of distortion and noise output. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.